The Normal Abdominal Aorta Ultrasound: Skills of carrying out Abdominal Aortic Aneurysm Assessment

Before starting to scan the aorta, it is helpful to understand the anatomy, which is shown in the image on the right. Note the branches of the coeliac axis and its relationship to the superior mesenteric artery (SMA).

  • The coeliac axis is 1-2 cm below the diaphragm
  • The superior mesenteric artery is 2 cm below the coeliac axis
  • The inferior mesenteric artery is 4 cm above the bifurcation
  • The aorta bifurcates at, or immediately below, the umbilicus (L4)

The maximum external diameter (measured from outer wall to outer wall) at different levels will vary:

  • 3 cm at the epigastrium
  • 1.5 cm at the bifurcation